Disk drives are standard devices for storing data. A disk drive typically includes platters (also known as disks) that the data are stored on and a read-write head that is used to write data onto the platters and to read the data from the platters. The read-write head is manufactured to include what is commonly known as a slider that has aerodynamic properties to fly over a platter. A slider flies over a location on a platter for the purpose of writing data to that location or reading data from that location. The distance between a slider and a platter that the slider is flying over is commonly referred to as a “fly height.”
Typically a slider includes a write head for writing data to a platter and a read sensor for reading data from the platter. Both write head and read sensors have dimension requirements, such as a throat-height for a write head and stripe-height for a read sensor. The air bearing surface (ABS) of a slider provides the aerodynamic properties that enables the slider to fly over a platter and to be positioned over a desired location on the platter. A write head is also commonly known as a writer. A read sensor is also commonly known as a read head or a reader.
In order for a slider as well as the read sensor and the write head to function properly, a slider's ABS after lapping needs to be flat and smooth. A flat and smooth ABS provides a foundation for achieving desired aerodynamic properties, as will become more evident. Further the write and read heads need to have appropriate dimensions.
A component or a part of a component which is ultimately manufactured into a slider, as will become more evident, shall be referred to herein as a “pre-slider.” FIG. 1 depicts part of a conventional process for manufacturing a pre-slider. Wafers are used in manufacturing read write heads and the associated pre-sliders.
The wafers can be cut into rows which are lapped in order to provide a flat and smooth ABS for the pre-sliders as well as to achieve target dimensions, such as the stripe height for the read head and throat-height for writer. Lapping can be performed in multiple stages using, for example, progressively finer grained lapping pads to achieve a smooth ABS and desired dimensions. In order to achieve optimized read/write performance in a disk drive, low fly heights, such as 10 nanometers or less, are desired. Patterns can be fabricated on the lapped ABS as a part of achieving desired aerodynamic properties. Among other things, a flat and smooth ABS provides a foundation for building the pattern on the lapped ABS in order to achieve desired fly heights.
FIG. 1 depicts a pre-slider 110 after lapping has been performed. Although pre-slider 110 can be a part of a row, FIG. 1 depicts the pre-slider 110 in isolation for the sake of illustration. Pre-slider 110 includes an overcoat 112 and a substrate 114. The overcoat 112 can be made of alumina. The read sensor 116 and the write head 118 are built inside of the overcoat 112.
A high temperature can be applied to the pre-sliders to align the magnetic moments of the material from which sensors 116 are made. More specifically, a high temperature can be applied to the pinning layer of the read sensor 116. The process of applying a high temperature to the pre-sliders is commonly referred to as annealing 120. Pre-slider 130 has been annealed 120. Pre-slider 130 includes an overcoat 132 and substrate 134. As a result of being annealed 120, the overcoat 132 has expanded resulting in a protrusion 136. Since the ABS of a pre-slider must be flat and smooth in order for a read write head to glide properly over a platter, the protrusion 136 causes the pre-slider 130 to be unsuitable. Only those pre-sliders that do not have protrusions can continue in the manufacturing process to become acceptable sliders.